Kane is on a pace to score ~30 goals over an 82 game season. He plays LW -- not exactly a position we have depth at (unless you have faith in Ennis lasting a season). He's one of the fastest skaters on the team, and getting slower isn't typically a recipe for success. He can be aggravating to watch at times but he's not the problem with this team.
If you want to ditch Kane for his off-ice antics, yeah, I get that. But trading him for D doesn't make sense when we traded a 1st pair D to get him in the first place.